title: The origin of long-period lattice spacings observed in iron-carbide nanowires encapsulated by multiwall carbon nanotubes.
abstract: Structures comprising single-crystal, iron-carbon-based nanowires encapsulated by multiwall carbon nanotubes self-organize on inert substrates exposed to the products of ferrocene pyrolysis at high temperature. The most commonly observed encapsulated phases are Fe₃C, α-Fe, and γ-Fe. The observation of anomalously long-period lattice spacings in these nanowires has caused confusion since reflections from lattice spacings of ≥ 0.4 nm are kinematically forbidden for Fe₃C, most of the rarely observed, less stable carbides, α-Fe, and g-Fe. Through high-resolution electron microscopy, selective area electron diffraction, and electron energy loss spectroscopy we demonstrate that the observed long-period lattice spacings of 0.49, 0.66, and 0.44 nm correspond to reflections from the (100), (010), and (001) planes of orthorhombic Fe₃C (space group Pnma). Observation of these forbidden reflections results from dynamic scattering of the incident beam as first observed in bulk Fe₃C crystals.With small amounts of beam tilt these reflections can have significant intensities for crystals containing glide planes such as Fe₃C with space groups Pnma or Pbmn.
authors.affiliation: School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
authors.forename: Filippo S
authors.initials: FS
authors.lastname: Boi
authors.forename: Gavin
authors.initials: G
authors.lastname: Mountjoy
authors.forename: Zofia
authors.initials: Z
authors.lastname: Luklinska
authors.forename: Liam
authors.initials: L
authors.lastname: Spillane
authors.forename: Lisa S
authors.initials: LS
authors.lastname: Karlsson
authors.forename: Rory M
authors.initials: RM
authors.lastname: Wilson
authors.forename: Anna
authors.initials: A
authors.lastname: Corrias
authors.forename: Mark
authors.initials: M
authors.lastname: Baxendale